


a river between

by theloosegoose



Category: BanG Dream! Girl's Band Party! (Video Game), Promare (2019)
Genre: Aged-Up Character(s), Angst, F/F, Gen, Sibling Incest, Sibling Rivalry, Spoilers, Unresolved Emotional Tension, mentions of human experimentation
Language: English
Status: Completed
Published: 2019-09-21
Updated: 2019-09-21
Packaged: 2020-10-25 04:13:37
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,402
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20717903
Author URL: https://archiveofourown.org/users/theloosegoose/pseuds/theloosegoose
Summary: a SayoHina Promare AU.set in the Promare universe, HUGE LORE/PLOT POINT SPOILERS FOR PROMARE, you have been warned.also a "what if Sayo and Hina had never worked out their issues" AU.





	a river between

**Author's Note:**

> I definitely ship SayoHina and I was intending for this entire fic to be read w/ that lens. While nothing overtly romantic fit the tone of this piece, I'm tagging for incest anyways just to be safe. 
> 
> originally I wanted to write Heris/Aina but somehow my siscon muse led me towards SayoHina.
> 
> anyhow this is an indulgent import of Sayo and Hina into Heris and Aina's roles but w/ their own dynamic, yes the rest of Pastel*Palettes is on Burning Rescue, no the governor is not anybody from the Bandori universe, etc. to quote a friend of mine, "you didn't pay me to do worldbuilding"
> 
> <s>also why isn't there a Bandori appellation guide. I don't know who calls who by what so I just guessed.</s>  
EDIT: APPARENTLY THERE IS, but it's not on the wiki. but now we know. [Here you go. ](https://www.reddit.com/r/BanGDream/comments/8l572r/bandori_name_reference_chart/)

Another medal, another celebration.

Another atrocity committed in the name of scientific progress. It would all be worth it in the end - at least that’s what Sayo Hikawa told herself, because if it wasn’t, was there any reason to keep going? Being promoted to lead researcher on a classified project was an honor many of her peers would kill for, but if only they knew what happened behind closed doors. 

She was the new rising star of the science world; now widely regarded as a pioneer, a prodigy. How ironic. 

Sayo wondered if Hina would hate her if she ever knew the truth, but she was already too deep in this web of lies to back out. It was fine. Everything would be okay in the end, as long as Sayo could create a world where they could start over. 

\--

Hina had been the real prodigy, able to do almost anything seemingly without trying. Hina was the one with the good ideas, constantly thinking out of the box, while Sayo set about divining the method within the madness and translating Hina’s constant mumblings into hypotheses and tests and meticulous sheets of data. Sayo was the one with the stubborn dedication. The one who trusted cold, hard logic.

They would have been the perfect team. 

But more and more, Sayo found herself both captivated by and resenting Hina. What did science even mean to Hina? Did their countless failed experiments together even matter to Hina? Everything Sayo tried, Hina would attempt and surpass her easily, like an inescapable mirror. Would there ever be anything that Sayo could completely call her own - a place that Hina could never reach?

Rather than become Sayo’s shadow, Hina was a light trailing after her, unwittingly casting a shadow on Sayo herself. 

Even the latest development in her work was made on the backs of a theory Hina had proposed in passing years ago, Sayo noted wryly. 

\--

The day Sayo left for university was a day she’d never forget; her parents’ proud smiles, Hina’s crying one, yet also bearing the same proud smile-

It was maddening how, even after Sayo had gone to all this to distance herself from her sister, Hina still held nothing but genuine adoration.

Sayo was leaving for a top school with a prestigious, internationally recognized science program. Part of her still chafed at how the college advisor had recommended it to Hina at first, and how Hina had gotten a higher examination score. But it was Sayo who had earned the grades for it. Sayo, who had the project portfolio the admissions committee had deemed worthy. Sayo, whose slow and steady approach had won out for once. 

Sayo boarded the train, and didn’t look back as Hina waved.

\--

Hina wrote. 

Emails and texts about how she dropped out of the local university to join Burning Rescue. About how she was put on the logistical support and research team and that was fine and all but wouldn’t it be exciting if she could be out on the frontlines saving people?

_ That’s dangerous, don’t just jump into things without thinking, _ Sayo had replied, but she knew that wouldn’t stop Hina.

Like with everything Hina did, she was excellent at it. Her unconventional approach was a handful for her superiors at first but soon her team made rescue after rescue, and earned a reputation for being the most reliable rookies.

_ Aya-chan is always afraid to fly close to the burning buildings, _ Hina wrote.

_ Any normal person would be, _Sayo replied.

More mundane life updates here or there, sometimes pictures of food from the pizzeria down the street from the Hikawa residence (_ they have a new menu, let’s go when you come back, onee-chan _ ). Sometimes selfies with her team members. Sometimes complaints about the paperwork she had to do after each mission ( _ it’s so boring… not boppin’ at all _).

Sayo was grateful when classes and her research fellowship finally picked up. It was easier to lose herself in her studies than respond to Hina. Why did Hina insist on being an ever-present reminder of what Sayo was not? Why was she there, casually shining even from hundreds of miles away. _ You have options, this is all I have. This is all I’ll ever be. _

\--

Hina’s texts came less and less frequently as the years went by. But when they came, there was an increasing unspoken weariness.

_Onee-chan, we couldn’t save everybody today. Was I wrong for wanting to? _

Another week.

_ Chisato-chan said that some things are impossible, but we try our best anyway! Because that’s what it means to be alive. _

Another month.

_ I think sometimes I understand how it feels not to get it right on the first try. _

Sayo always read Hina’s texts at some ungodly hour of the night after spending the entire day at the lab, but never knew how to respond. At this point she wasn’t sure if she should. She supposed she should have felt some gratification at Hina, the shining genius, realizing in the end, she was just human. Sayo banished the thought as soon as it arrived; what kind of terrible person was she? 

It wasn’t as if Sayo couldn’t understand. The deeper she delved into science, the more she was aware of its limitations, of the problems she couldn’t fix. She hadn’t been naive enough to think otherwise even as a teen, but it was one thing to note something as reality and another to confront it firsthand. It was impossible to save everybody after all, but at least Hina was out there trying her hardest. What was she doing, behind closed doors in the safety of her lab? 

Maybe this world was terrible; it was crumbling, after all. The magma surges were getting stronger by the day, and this top secret project was possibly humanity’s - or more accurately a select few’s - salvation. It wasn't something Sayo was proud of, but her work had guaranteed her family a spot aboard when the chosen few were to finally leave the doomed Earth behind.

Maybe, finally, she could be honest with Hina. And apologize. They could start over in a world that wasn’t about to turn to ash.

_Onee-chan, I miss you. _

_ I miss you too, _Sayo typed.

She didn’t send it.

And soon, Sayo would have blood on her hands.

\--

_ Are the Burnish really that bad? _

Sayo turned off her phone, trying not to wince as her lab assistants fastened the sedated, disheveled man to the machine. Another signal, another button press, another Burnish’s life evaporated before her, another person sacrificed for the sake of what? Scientific progress? Humanity? Such ideals seemed like flimsy excuses.

_ Eve-chan said they could be people just like us. Maya-chan said maybe they’re only scary because we don’t understand them. _

The first time Sayo saw a body crumble to ash, she promptly threw up on the sterilized floor.

The governor had patted her on the back and chuckled wryly. It would never get better, but it was necessary to save people. To save Hina. She couldn’t turn her back on everything she’d worked on. 

_ Maybe we could talk to them first, onee-chan. _

There it was; Hina’s curiosity. Hina always had another path, always thought of other possibilities, maybe Hina was right after all, maybe all these horrors could be avoided, maybe there was another way-

No, it’s too late. _ I have to do this, _ Sayo thought.

_ Maybe they don’t understand why they have to burn things. Maybe they get sad too when their friends die. _

\--

Sayo stared straight ahead as journalists took her photo, and answered with the same rehearsed responses as reporter after reporter flocked to her.

The party was too long, and the lights were too bright. The medal was heavy, but nothing compared to the weight of everything Sayo had done, and would continue to do.

_ Why did you do it, onee-chan? Why did those people have to- _

Several nights Sayo woke in a cold sweat, Hina’s disappointed and hurt face burned into her mind. 

_Onee-chan, I saw you on TV! Congrats! _

Sometimes Sayo wondered if she had just talked to Hina years ago, maybe she would have had the courage to walk away when she saw the project proposal. Maybe.

_ Are you coming home for Christmas? We all miss you, but I miss you the most! _

_ No, _Sayo replied. 

_ I miss you too, _Sayo typed.

This time, she sent it.

**Author's Note:**

> fun fact, Hikawa (氷川) literally means "ice river" hence the title. I wanted to go w/ "a frozen river between" but it wasn't as catchy.


End file.
